Keeping belly bacteria balanced is key, but a challenge for cancer patients

Learn about the important role gut bacteria play in our overall health and in certain diseases, including cancer.

The human colon is a teeming sea alive with millions of bacteria. In this briny deep within the gut swim trillions of bacteria from hundreds of different species. Some species of bacteria, if left unchecked, could cause infections or disease. Others promote good digestion and help fight infection. Doctors and scientists have discovered the benefits of maintaining a healthy balance of good and bad bacteria in the colon and the role our gut bacteria, also called microbiota, microbiome or gut flora, plays in many diseases, including cancer. “The normal bacterial balance is when there are significantly more good bacteria to overpower the bad bacteria,” says Pankaj Vashi, MD, Gastroenterologist at our Chicago hospital. In cancer patients, maintaining that balance is often a challenge, potentially impacting treatments and leading to difficult side effects. That’s why, experts say, it’s important for cancer patients to be aware of the dangers, and to give them tools to help prevent and manage them.

Cancer may wreak havoc on the human microbiota. The disease strains the immune system, which may allow bad bacteria in the gut to flourish. Antibiotics used to fight infection also may kill good bacteria in the colon. “Antibiotics are like a grenade,” says Zach Breeding, registered and licensed Advanced Clinical Oncology Dietitian at our Philadelphia hospital. “They can destroy so much bacteria in your gut, both good and bad.” To further complicate matters, cancer treatments may lead to a pronounced imbalance of microorganisms, a condition called dysbiosis. For instance:

  • Surgery to remove part of the colon also removes bacteria and some of the tissue in which they live.
  • Radiation therapy may damage or inflame tissue in the colon.
  • Chemotherapy, especially, may wreak havoc on the gut. Treatments may kill bacteria that aids digestion, often leading to diarrhea, which further depletes good bacteria.

“Whenever patients get sick from chemotherapy and get diarrhea, they lose a lot of good bacteria,” Dr. Vashi says. “And we have patients who take multiple antibiotics that destroy a lot of good bacteria. These can lead to different infections, including the most notorious one, which is C. difficile.” Clostridium difficile infection, known simply as C. diff, is marked by inflammation in the colon, often brought on by disrupted gut flora and a compromised immune system. C. diff infections are diagnosed in about 10 percent of cancer patients. Research indicates cancer patients with C. diff may have poorer outcomes than those who don’t have the infection. To treat patients with C. diff, Dr. Vashi may consider a fecal transplant procedure, in which feces from a healthy donor is implanted into the colon of the infected patient. “We see some dramatic responses in which the diarrhea is gone in as little as 24 hours,” Dr. Vashi says. “Many times, they don’t get recurrent infections.”

To help reduce the effects of chemotherapy on the microbiome, doctors and nutritionists often turn to prebiotics to bolster the microbiota and probiotics to restore good bacteria lost or destroyed by treatment. “ Before therapy, I’m always recommending a good, wholesome diet that contains a lot of plant-based foods—fruits, vegetables, beans, legumes,” Breeding says. “These foods are high in prebiotics, the food for the probiotics. Anything that has roughage and is cooked al dente, such as beans or broccoli, which are high in insoluble fiber, will allow probiotics to thrive.” During and after therapy, probiotic supplements that contain multiple types of microorganisms help restore the good bacteria in the gut. “When you are in dysbiosis, you can’t just throw yogurt at that,” Breeding says. “You don’t need just a little bit of probiotics; you need a ton.”

What is the human microbiome?

Here’s some of what we know so far, according to the Human Microbiome Project:

  • Human microbiota is made of trillions of viruses, fungi and other microorganisms.
  • The human microbiota has 10 times more microorganisms than human cells.
  • Microorganisms make up about 3 percent of our total body mass, or about six pounds of a 200-pound adult.
  • Imbalances in human gut flora have been linked to autoimmune diseases such as Crohn’s disease and multiple sclerosis, obesity and heart disease.

In 2008, the National Institutes of Health established The Human Microbiome Project to research and compile data to study the microbiome’s impact on disease. “It has been found that bacteria play a role in multiple diseases,” Dr. Vashi says. “There are studies now that are showing that changes in bacterial flora can contribute to developing conditions, such as irritable bowel syndrome and colitis. Fascinating work has been done where we are learning more and more about gut microbiome playing a major role in many conditions, including obesity.”

While evidence suggests dysbiosis can lead to autoimmune diseases and other conditions, “there is not strong data that shows a direct connection to gut bacteria causing cancer,” Dr. Vashi says. However, research has shown connections between gut flora and cancer risk factors and the effectiveness of treatments. Multiple studies have found that the composition of a patient’s gut bacteria may influence the performance of immunotherapy drugs called checkpoint inhibitors. In one of those studies, melanoma patients who had good bacteria in their guts had better responses to anti-PD-1 immunotherapy drugs than patients with bad gut bacteria. “An important and clinically relevant issue is whether manipulation of the intestinal microbiome could turn patients [who] are nonresponsive to immune checkpoint blockade into responders,” Christian Jobin, PhD, of the University of Florida, writes in an editorial quoted by the National Cancer Institute’s Cancer Currents Blog.

A gut bacteria imbalance sometimes causes health problems that may raise the risk of cancer. For instance, a diet high in meats and processed foods and lacking in fresh vegetables may damage gut flora and increase the risk of certain gastrointestinal cancers, including colorectal cancer. Also, an imbalance in the microbiome may lead to obesity, which is a risk factor for many cancers, including breast cancer and prostate cancer. “We know the microbiome can play a major role in developing obesity,” Dr. Vashi says. “And we know that obesity plays a role as a risk factor in certain cancer types. So, there is a strong argument that people who have bad microbiomes are likely to become more obese, which may make them more susceptible to developing more cancer types.”

What can you do? Tips for maintaining your microbiome

Expand your menu. Gut flora is a diverse collection of bacteria. A diverse menu of foods encourages the growth of many types of bacteria, which makes for a healthy microbiota.

Try fermented foods. These foods contain and feed probiotics and help promote healthy gut bacteria. Fermented foods include yogurt, kimchi, sauerkraut, miso and tempeh.

Eat more fruits, vegetables and beans. Limiting animal fats and eating a plant-based diet will increase fiber intake and promote a healthy gut.

Stick with whole grains. Processing often strips fiber and nutrients from many grains, such as wheat and rice. Whole grains are rich in fiber and good for the gut.

Avoid artificial sweeteners. Research indicates that sugar substitutes, such as saccharin and aspartame, may promote obesity rather than prevent it, and damage gut flora.

Talk to your doctor. Ask questions about antibiotics you may be prescribed, and talk to your doctor about the benefits of a probiotic supplement.

Learn about prebiotics. Probiotics have long been promoted to improve gut health, but prebiotics also are important. Examples of prebiotics include leeks, onions, garlic, asparagus, spinach, bananas, oats and beans.

Consider your lifestyle. Quit smoking. Drink alcohol in moderation. Get enough restful sleep. Get enough exercise. Eat a balanced diet. A healthy life often means a healthy gut, and a healthy gut helps promote a healthy life.

Sources: Physicians Committee for Responsible Medicine; healthline.com

Learn more about supportive care therapies and side effect management.